Commonly used by large companies to tailor the work environment to employee's personality traits, the Myers-Briggs test has not been scientifically proven to be an accurate indicator of a person's personality. The test seems to ignore the fact that personalities are not defined as one or the other, but, rather constructed of bits and pieces of all the personality types.
The science podcast Skeptoid points out that the results are also positive and encouraging, never pointing out the negative aspects of a particular personality type. This can lead people to believe in the accuracy of the test because they like what they read. Overall, the test is a fun look at personality types, but there is not scientific or theoretical evidence that it is accurate or reliable.